Magnetic tachometer.



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APPLIQATION FILED 00T. 1, 1902.

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tio. 745,468.

UNITED STATES Fatented December 1, 190911 PATENT ENCE..7

MAGNETIC lTACHOIVIETER.

SPECIFICATION forming part 0f Letters Patent O. 745,468, dated December1, 1903.

Application filed October 1, 1902. Serial No. 125 ,468. (No model.) d lTo @ZZ whom, t may con/cern! l Be it known that we, ARTHUR P. WARNER,residing at Chicago, in the county of Cookand State of Illinois, andCHARLES H. WARNER, residing at Beloit, county of Rock, State ot'Wisconsimcitizens of the United States, have invented a new and usefulImprovement in Magnetic Tachometers, of which the following is aspecification.

Thisinvention relates to magnetic tachometers. A

The object of the invention is to provide a device which is simple andecicient for meas uring the speed of rotation ofshafts.

A further object of the invention is to provide a magnetic device of theclass described which is capable of accurate calibration.

A further object of the invention is to provide a device of thecharacter referred "to which is simple and efficient and wherein thespeed of rotation to be measured will be directly indicated.

Other objects of the invention will appear more fully hereinafter. 4

The invention consists substantially in the construction, combination,location, and arrangement of parts, all as will be more fullyhereinafter set forth, as'shown in the accompanying drawings, andfinally pointed out in the appended claims. Y

Referring to the accompanying drawings and to the various views andreference-signs appearing thereon, Figure l is a View in side elevationof a device embodying the principles of my invention. Fig. 2 is a viewin central longitudinal section of the same. Fig. 3 is a detail view infront elevation of the magnet shown in Fig. 2.

In the drawings reference-sign A designates a casing provided with a hubB,` internally threaded and adapted to receive an eX- teriorly-threadedblock C.

The shaft of the instrument is indicated by reference-sign D and isjournaled within bearing-block C upon ball-bearings, the balls E beingreceived in raceways F, formed in bearing-block C and retained thereinby means of cone-collars G, mounted upon the instrul ment-shaft D.

coupled in any suitable or convenient manner to shaft D of theinstrument. The position of the bearing-block C may be adjustedwithin'hub B in any'convenient manner-Vas, for instance, by means ofset-nut .I -and similarly the cone-hearings G of the ball-bearing may beadjusted by nut K. Mounted upon shaft D to rotate therewith is apermanent magnet L. A convenient arrangement is shown wherein shaft D isprovided with a threaded extension M, adapted to be screwed into acentral opening through permanent magnet L. Suitably fixed within casingA is a mass N of iron or other suitable magnetic material. In practicewe prefer to employ this mass of iron in the form of a ring having acentral opening therethrough. We also prefer to dish the mass of iron ormagnetic material on the face thereof presented toward the poles ofmagnet L.` This enables us to secure greater rigidity and strength andto obtain better results, and we suitably form the pole-faces of magnetL to lie in planes parallel withl the adjacent surface of the magneticmass. Suitably interposed between the opposed or juxtaposited faces ofthe mass N and magnet Lis a rotary disk O, of suitable conductingmaterial-such, for instance, as aluminium-said disk having a peripheralii'ange P, suitably graduated, as indicated at Q, Fig. l. Through thecasing A we arrange an opening R, so as to disclose therethrough thegraduations Q upon the flange of disk O. The disk O may be mounted torotate freely in any suitable or convenient manner. In the form shown,to which, however, our invention is not to be limited or restricted, thescale-disk O ismounted upon to rotate with a stud bearing -pin S, theends of which are pointed and journaled in seats formed in screw-plugs Tand U. Screw-plug T is mounted in an arm A', suitably secured to the xedmass N or other stationary part. The screw-plug U is mounted centrallyin a disk or shield plate B', ofnon-magnetic material, which is inter`posed between scale-disk O and magnet L and is stationarily held withincasing A. Rotative movement of disk O is yieldingly opposed in anysuitable or convenient manner and in cooperative proportion to therotative torque imparted to saiddisk. In the form ARTHUR P. WARNER, OFCHICAGO, ILLINOIS, AND CHARLES H. WARNER, OF BELOIT, gWISCONSIN. l

IOO

shown we employ a hair-spring C, having one end fixed to the mass N andthe other attached to the pin-shaft S.

In practice the casing A, shield disk or plate B', and arm A we preferto make of non-magnetic material-such, for instance, as brass-though wedo not desire to be limited in this respect. The shield plate or disk Bis provided with a lateral iiange D', which extends over and around theflange P of scale plate or disk O and rests against a shoulder(indicated at E) formed on the inner` surface of casing A, said flangebeing backwardly turned from said shoulder and suitably secured to themass N. The parts are inclosed within casing A and securely clamped andheld in place therein in any suitable manner-as, for instance,-by meansof a screw cap or cover F', screwed into the threaded iiange of casingA, as clearly indicated in the drawings.

By suitably adjusting the set-nut J the longitudinal displacement ofbearing-block C, and consequently' of shaft D, may be accuratelyadjusted to cause the pole-faces of magnet L to be adjusted nearer to orfarther from I the magnetic mass N. This is a valuable feature, inasmuchas it enables us to accurately calibrate the scale-disk O.

The operation of the device is as follows: When the instrument-shaft Dis connected to a rotative shaft H and rotations are imparted thereto,such rotations are imparted to magnet L. By means of currents ormagnetic effeet created in the magnetic circuit, which includes themagnet L and the mass of magnetic material N, a rotative tendency isimparted to scale-disk O in the direction of rotation of magnet L and indirect proportion to the rotative speed of said magnet, such rotativetendency being opposed by spring C', and this opposition should be sorelatively proportioned with respect to the magnetic effect created bythe rotation of magnet L as to cause the scale-disk O to revolve to aneX- tent in direct proportion to the speed of rotation of shaft L, andhence when said scaleplate is properly calibrated the exact speed ofrotation of the shaft will be indicated in the graduations disclosedthrough the opening R in casing A, the latter being held stationary byhand or otherwise.

The shield-plate B incloses the rotative scale-disk O so far as therotating magnet is concerned and serves the important purpose ofprotecting said disk against danger of rotative displacement under theinfluence of air-currents created by the rotations of the magnet. Inthis manner the entire rotative tendency imparted to the scale-disk isdue solely to the electromagnetic effect produced, and hence moreaccurate and perfect results are secured.

From the foregoing description it will be seen that we provide anexceedingly simple and efficient magnetic tachometer, the calibration ofwhich can be adjustably regulated and wherein the construction is simpleand the readings are direct.

Having now set forth the object and nature of our invention and aconstruction embodying the principles thereof, what we claim as new anduseful and of our joint invention, and desire to secure by LettersPatent, is-

1. In a tachometer, a magnet and a magnetic mass, these` parts mountedfor relative rotation, said mass having the surface thereof presentedtoward the pole-faces of the magnet lying in a plane inclined relativelyto the axis of such rotation, the pole-faces of said magnet being shapedto present a surface parallel to the inclined surface of said mass, andan independently-rotative scale-disk interposed between said mass andmagnet, as and for the purpose set forth.

2. In a tachometer, a magnet, a magnetic mass, one of these partsmounted to rotate, av

freely-rotative scale-disk interposed between said mass and magnet, andmeans for protecting said disk from the effects of air-currents createdby said rotating part, as and for the purpose set forth.

3. The combination with a shaft, of a magnet connected thereto to rotatetherewith, a magnetic mass in proximity to which said magnet rotates,and an independently-revo-A 'mass and magnet, and means for protectingsaid disk from air-currents created by the rotation of said magnet, asand for the purpose set forth. g

4. In a tachometer, a magnet and a magnetic mass, one of these partsmounted to rotate with the shaft the speed of which is to be measured,means for adjusting the poles of said parts toward and from each other,and a scale-disk interposed between said parts and revolubly mounted,and means for opposing the rotary movement of said disk, as and for thepurpose set forth.

5. In a tachometer, a magnet and a magnetic mass, one of these partsmounted to rotate with the shaft the speed of which is to be measured, ascale-disk interposed between said magnet and magnetic mass, said diskbeing mounted for independent rotative movement, means for yieldinglymaintaining said disk in a normal or initial position, and means foradjusting the reluctance of the magnetic circuit of said magnet andmass, whereby said scale-disk may be calibrated, as and for the purposeset forth.

G. In a tachometer, a magnet and a magnetic mass, said parts mounted forrelative rotation, in combination with a scale-disk as sociated withsaid parts and mounted for independent rotative movement, means normallyoperating to maintain said disk in initial or normal position, and meansfor adj usting the reluctance of the magnetic circuit of said magnet andmass, whereby said scaledisk may be accurately calibrated, as and forthe purpose set forth.

7. In a tachometer, a magnet and a mag IOO IIO

part, and means for yieldingly opposing the rotary movement of saiddisk, as and for the purpose set forth.

9. In a taehometer, a casing having a hub, a bearing-block adjustabiymounted in said hub, a shaft jonrnaled upon ball-bearings in saidbearing-block, and carrying a magnet, said shaft connected to rotatewith the rotating part the speed of which is to be measured, a magneticmass arranged Within saideasing and provided with an arm, a platearranged within said casing and interposed between said mass andmagnet,bearings carried by said arm and plate, adisk interposed betweensaid plate and mass, a supporting-pin therefor, said pin jonrnaled inthe bearings in said arm and plate whereby said disk is permittedindependent rotation, a spring eonneeted at one end to said mass and atthe other end to said pin, said disk carrying graduations; all combinedand arranged as and for the purpose set forth. Y

In Witness whereof ARTHUR P. WARNER hashereunto set his hand this 23dday of September, 1902, in the presence of the subscribing Witnesses,and the said CHARLES H. WAR- NER has set his hand this 25th day ofSeptember, 1902, inthe presence of the subscribing Witnesses.

ARTHUR P. WARNER. CHARLES H. WARNER.

Witnesses for Arthr P. Warner:

CEAS. H. SEEM, EDWIN C. SEMPLE.

Witnesses for Charles H. Warner:

B. L. LAWSON, E. BRITTAN.

